Help

So that I don't look totally retarded, how can I make my license plate stop rattling? I put some old sponge behind the place, but that really didn't help too much.

I have a '96 Altima w/ a MTX T4250D Amp and two MTX T6124A 12" Subs.

to make this short, I applyed a sheet of dynomat behind my license plate. I stopped ratteling but when my subs are hitting really hard it rattles again...

I noticed that it's not my plate that's rattling but my rear bumper. I removed the plate, then used a screw to attach the bumper to the body just behind the plate. then put the plate back.

no rattling in my car now